Apparatus and methods for electrochemical processing of microelectronic workpieces

ABSTRACT

A processing chamber comprising a reaction vessel having an electro-reaction cell including a virtual electrode unit, an electrode assembly disposed relative to the electro-reaction cell to be in fluid communication with the virtual electrode unit, and an electrode in the electrode assembly. The virtual electrode unit has at least one opening defining at least one virtual electrode in the electro-reaction cell. The electrode assembly can include an electrode compartment and an interface element in the electrode compartment. The interface element can be a filter, a membrane, a basket, and/or another device configured to hold the electrode. The interface element, for example, can be a filter that surrounds a basket in which the electrode is positioned.

CROSS-REFERENCE TO RELATED APPLICATIONS

The applications claims the benefit of U.S. Application No. 60/316,597filed on Aug. 31, 2001.

TECHNICAL FIELD

This application relates to reaction vessels and methods of making andusing such vessels in electrochemical processing of microelectronicworkpieces.

BACKGROUND

Microelectronic devices, such as semiconductor devices and fieldemission displays, are generally fabricated on and/or in microelectronicworkpieces using several different types of machines (“tools”). Manysuch processing machines have a single processing station that performsone or more procedures on the workpieces. Other processing machines havea plurality of processing stations that perform a series of differentprocedures on individual workpieces or batches of workpieces. In atypical fabrication process, one or more layers of conductive materialsare formed on the workpieces during deposition stages. The workpiecesare then typically subject to etching and/or polishing procedures (i.e.,planarization) to remove a portion of the deposited conductive layersfor forming electrically isolated contacts and/or conductive lines.

Plating tools that plate metals or other materials on the workpieces arebecoming an increasingly useful type of processing machine.Electroplating and electroless plating techniques can be used to depositnickel, copper, solder, permalloy, gold, silver, platinum and othermetals onto workpieces for forming blanket layers or patterned layers. Atypical metal plating process involves depositing a seed layer onto thesurface of the workpiece using chemical vapor deposition (CVD), physicalvapor deposition (PVD), electroless plating processes, or other suitablemethods. After forming the seed layer, a blanket layer or patternedlayer of metal is plated onto the workpiece by applying an appropriateelectrical potential between the seed layer and an electrode in thepresence of an electroprocessing solution. The workpiece is thencleaned, etched and/or annealed in subsequent procedures beforetransferring the workpiece to another processing machine.

FIG. 1 illustrates an embodiment of a single-wafer processing station 1that includes a container 2 for receiving a flow of electroplatingsolution from a fluid inlet 3 at a lower portion of the container 2. Theprocessing station 1 can include an anode 4, a plate-type diffuser 6having a plurality of apertures 7, and a workpiece holder 9 for carryinga workpiece 5. The workpiece holder 9 can include a plurality ofelectrical contacts for providing electrical current to a seed layer onthe surface of the workpiece 5. The seed layer acts as a cathode when itis biased with a negative potential relative to the anode 4. Theelectroplating fluid flows around the anode 4, through the apertures 7in the diffuser 6, and against the plating surface of the workpiece 5.The electroplating solution is an electrolyte that conducts electricalcurrent between the anode 4 and the cathodic seed layer on the surfaceof the workpiece 5. Therefore, ions in the electroplating solution plateonto the surface of the workpiece 5.

The plating machines used in fabricating microelectronic devices mustmeet many specific performance criteria. For example, many processesmust be able to form small contacts in vias that are less than 0.5 μmwide, and are desirably less than 0.1 μm wide. The plated metal layersaccordingly often need to fill vias or trenches that are on the order of0.1 μm wide, and the layer of plated material should also be depositedto a desired, uniform thickness across the surface of the workpiece 5.

One concern of many processing stations is that it is expensive tofabricate certain types of electrodes that are mounted in the reactionvessels. For example, nickel-sulfur (Ni—S) electrodes are used todeposit nickel on microelectronic workpieces. Plating nickel isparticularly difficult because anodization of the nickel electrodesproduces an oxide layer that reduces or at least alters the performanceof the nickel plating process. To overcome anodization, nickel can beplated using a chlorine bath or an Ni—S electrode because both chlorineand sulfur counteract the anodizing process to provide a more consistentelectrode performance. Ni—S electrodes are preferred over chlorine bathsbecause the plated layer has a tensile stress when chlorine is used, butis stress-free or compressive when an Ni—S electrode is used. Thestress-free or compressive layers are typically preferred over tensilelayers to enhance annealing processes, CMP processes, and otherpost-plating procedures that are performed on the wafer.

Ni—S electrodes, however, are expensive to manufacture in solid, shapedconfigurations. Bulk Ni—S material that comes in the form of pellets(e.g., spheres or button-shaped pieces) cannot be molded into thedesired shape because the sulfur vaporizes before the nickel melts. Thesolid, shaped Ni—S electrodes are accordingly formed usingelectrochemical techniques in which the bulk Ni—S material is dissolvedinto a bath and then re-plated onto a mandrel in the desired shape ofthe solid electrode. Although the bulk Ni—S material only costsapproximately $4-$6 per pound, a finished solid, shaped Ni—S electrodecan cost approximately $400-$600 per pound because of the electroformingprocess.

Another concern of several types of existing processing stations is thatit is difficult and expensive to service the electrodes. Referring toFIG. 1, the anode 4 may need to be repaired or replaced periodically tomaintain the necessary level of performance for the processing station.In many cases, an operator must move a head assembly out of the way toaccess the electrode(s) in the reaction vessel. It is not only timeconsuming to reposition the head assembly, but it is also typicallyawkward to access the electrodes even after the head assembly has beenmoved. Therefore, it is often difficult to service the electrodes in thereaction vessels.

SUMMARY

The present invention is directed toward processing chambers and toolsthat use processing chambers in electrochemical processing ofmicroelectronic workpieces. Several embodiments of processing chambersin accordance with the invention provide electrodes that use a bulkmaterial which is much less expensive than solid, shaped electrodes. Forexample, these embodiments are particularly useful in applications thatuse nickel-sulfur electrodes because bulk nickel-sulfur materials aremuch less expensive than solid, shaped nickel-sulfur electrodes that aremanufactured using electroforming techniques. Several embodiments ofprocessing chambers are also expected to significantly enhance theability to service the electrodes by providing electrode assemblies thatare not obstructed by the head assembly or other components in areaction chamber where the workpiece is held during a processing cycle.Many of the embodiments of the invention are expected to provide thesebenefits while also meeting demanding performance specifications becauseseveral embodiments of the processing chambers have a virtual electrodeunit that enhances the flexibility of the system to compensate fordifferent performance criteria.

One embodiment of the invention is directed toward a processing chambercomprising a reaction vessel having an electro-reaction cell including avirtual electrode unit, an electrode assembly disposed relative to theelectro-reaction cell to be in fluid communication with the virtualelectrode unit, and an electrode in the electrode assembly. The virtualelectrode unit has at least one opening defining at least one virtualelectrode in the electro-reaction cell. The electrode assembly caninclude an electrode compartment and an interface element in theelectrode compartment. The interface element can be a filter, amembrane, a basket, and/or another device configured to hold theelectrode. The interface element, for example, can be a filter thatsurrounds a basket in which the electrode is positioned.

In a more particular embodiment, the electrode comprises a bulkelectrode material, such as a plurality of pellets. The bulk electrodematerial can be contained in a basket, a filter, or a combination of abasket surrounded by a filter. In another embodiment, the electrodeassembly comprises a remote electrode compartment that is outside of theelectro-reaction cell so that a head assembly or the virtual electrodeunit does not obstruct easy access to the electrode in the electrodecompartment. In an alternate embodiment, the electrode assembly ispositioned in the electro-reaction cell under the virtual electrodeassembly, and the electrode is a bulk material electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an electroplating chamber in accordancewith the prior art.

FIG. 2 is an isometric view of an electroprocessing machine having anelectroprocessing station for processing microelectronic workpieces inaccordance with an embodiment of the invention.

FIG. 3 is a cross-sectional view of an electroprocessing station havinga head assembly and a processing chamber for use in an electroprocessingmachine in accordance with an embodiment of the invention. Selectedcomponents in FIG. 3 are shown schematically.

FIG. 4 is a schematic diagram of a processing station for use in anelectroprocessing machine in accordance with an embodiment of theinvention.

FIGS. 5A and 5B are isometric views showing portions of a processingchamber in accordance with an embodiment of the invention.

FIG. 6 is a cross-sectional view of an embodiment of the processingchamber shown in FIG. 5A taken along line 6-6.

FIG. 7 is an isometric cross-sectional view showing another portion ofthe processing chamber of FIG. 5A taken along line 7-7.

FIG. 8 is a schematic diagram of an electroprocessing station inaccordance with another embodiment of the invention.

FIG. 9 is a schematic diagram of another embodiment of a processingstation in accordance with yet another embodiment of the invention.

DETAILED DESCRIPTION

The following description discloses the details and features of severalembodiments of electrochemical processing stations and integrated toolsto process microelectronic workpieces. The term “microelectronicworkpiece” is used throughout to include a workpiece formed from asubstrate upon which and/or in which microelectronic circuits orcomponents, data storage elements or layers, and/or micro-mechanicalelements are fabricated. It will be appreciated that several of thedetails set forth below are provided to describe the followingembodiments in a manner sufficient to enable a person skilled in the artto make and use the disclosed embodiments. Several of the details andadvantages described below, however, may not be necessary to practicecertain embodiments of the invention. Additionally, the invention canalso include additional embodiments that are within the scope of theclaims, but are not described in detail with respect to FIGS. 2-9.

The operation and features of electrochemical reaction vessels are bestunderstood in light of the environment and equipment in which they canbe used to electrochemically process workpieces (e.g., electroplateand/or electropolish). As such, embodiments of integrated tools withprocessing stations having the electrochemical processing station areinitially described with reference to FIGS. 2 and 3. The details andfeatures of several embodiments of electrochemical processing chambersare then described with reference to FIGS. 4-9.

A. Selected Embodiments of Integrated Tools with ElectrochemicalProcessing Stations

FIG. 2 is an isometric view of a processing machine 100 having anelectrochemical processing station 120 in accordance with an embodimentof the invention. A portion of the processing machine 100 is shown in acut-away view to illustrate selected internal components. In one aspectof this embodiment, the processing machine 100 can include a cabinet 102having an interior region 104 defining an interior enclosure that is atleast partially isolated from an exterior region 105. The cabinet 102can also include a plurality of apertures 106 (only one shown in FIG. 1)through which microelectronic workpieces 101 can ingress and egressbetween the interior region 104 and a load/unload station 110.

The load/unload station 110 can have two container supports 112 that areeach housed in a protective shroud 113. The container supports 112 areconfigured to position workpiece containers 114 relative to theapertures 106 in the cabinet 102. The workpiece containers 114 can eachhouse a plurality of microelectronic workpieces 101 in a “mini” cleanenvironment for carrying a plurality of workpieces through otherenvironments that are not at clean room standards. Each of the workpiececontainers 114 is accessible from the interior region 104 of the cabinet102 through the apertures 106.

The processing machine 100 can also include a plurality of clean/etchcapsules 122, other electrochemical processing stations 124, and atransfer device 130 in the interior region 104 of the cabinet 102.Additional embodiments of the processing machine 100 can includeelectroless plating stations, annealing stations, and/or metrologystations in addition to or in lieu of the clean/etch capsules 122 andother processing stations 124.

The transfer device 130 includes a linear track 132 extending in alengthwise direction of the interior region 104 between the processingstations. The transfer device 130 can further include a robot unit 134carried by the track 132. In the particular embodiment shown in FIG. 2,a first set of processing stations is arranged along a first row R₁-R₁and a second set of processing stations is arranged along a second rowR₂-R₂. The linear track 132 extends between the first and second rows ofprocessing stations, and the robot unit 134 can access any of theprocessing stations along the track 132.

FIG. 3 illustrates an embodiment of an electrochemical processingstation 120 having a head assembly 150 and a processing chamber 200. Thehead assembly 150 includes a spin motor 152, a rotor 154 coupled to thespin motor 152, and a contact assembly 160 carried by the rotor 154. Therotor 154 can have a backing plate 155 and a seal 156. The backing plate155 can move transverse to a workpiece 101 (arrow T) between a firstposition in which the backing plate 155 contacts a backside of theworkpiece 101 (shown in solid lines in FIG. 3) and a second position inwhich it is spaced apart from the backside of the workpiece 101 (shownin broken lines in FIG. 3). The contact assembly 160 can have a supportmember 162, a plurality of contacts 164 carried by the support member162, and a plurality of shafts 166 extending between the support member162 and the rotor 154. The contacts 164 can be ring-type spring contactsor other types of contacts that are configured to engage a portion ofthe seed-layer on the workpiece 101. Commercially available headassemblies 150 and contact assemblies 160 can be used in theelectroprocessing chamber 120. Suitable head assemblies 150 and contactassemblies 160 are disclosed in U.S. Pat. Nos. 6,228,232 and 6,080,691;and U.S. application Ser. Nos. 09/385,784; 09/386,803; 09/386,610;09/386,197; 09/501,002; 09/733,608; and 09/804,696, all of which areherein incorporated by reference.

The processing chamber 200 includes an outer housing 210 (shownschematically in FIG. 3) and a reaction vessel 220 (also shownschematically in FIG. 3) in the housing 210. The reaction vessel 220directs a flow of electroprocessing solution to the workpiece 101. Theelectroprocessing solution, for example, can flow over a weir (arrow F)and into the housing 210, from which the electroprocessing solution canbe recycled. Several embodiments of processing chambers are shown anddescribed in detail with reference to FIGS. 4-9.

The head assembly 150 holds the workpiece at a workpiece-processing siteof the reaction vessel 220 so that at least a plating surface of theworkpiece engages the electroprocessing solution. An electrical field isestablished in the solution by applying an electrical potential betweenthe plating surface of the workpiece via the contact assembly 160 andone or more electrodes located at other parts of the processing chamber.For example, the contact assembly 160 can be biased with a negativepotential with respect to the other electrode(s) to plate metals orother types of materials onto the workpiece. On the other hand, thecontact assembly 160 can be biased with a positive potential withrespect to the other electrode(s) to (a) de-plate or electropolishplated material from the workpiece or (b) deposit other materials ontothe workpiece (e.g., electrophoretic resist). In general, therefore,materials can be deposited on or removed from the workpiece with theworkpiece acting as a cathode or an anode depending upon the particulartype of material used in the electrochemical process.

B. Selected Embodiments of Processing Chambers For Use inElectrochemical Processing Stations

FIGS. 4-9 illustrate several embodiments of processing chambers inaccordance with the invention. FIG. 4, more specifically, is a schematicdiagram of an embodiment of a processing chamber 400 that can be usedwith the head assembly 150 in the processing station 120 in accordancewith one embodiment of the invention. The processing chamber 400 caninclude a housing or tank 410, a reaction vessel 412 in the tank 410,and an electrode assembly 414 outside of the reaction vessel 412. Theprocessing chamber 400 can also include a fluid passageway 416 throughwhich a processing solution can flow to the reaction vessel 412 from theelectrode assembly 414.

The reaction vessel 412 includes an electro-reaction cell 420 and avirtual electrode unit 430 in the electro-reaction cell 420. The virtualelectrode unit 430 can be a dielectric element that shapes an electricalfield within the electro-reaction cell 420. The virtual electrode unit430, for example, has an opening that defines a virtual electrode VE.The virtual electrode VE performs as if an electrode is positioned atthe opening of the virtual electrode unit 430 even though the physicallocation of the actual electrode is not aligned with opening in thevirtual electrode unit 430. As described in more detail below, theactual electrode is positioned elsewhere in contact with an electrolyticprocessing solution that flows through the electro-reaction cell 420.The electro-reaction cell 420 can be mounted on a flow distributor 440that guides the flow of processing solution from the fluid passageway416 to the electro-reaction cell 420.

The electrode assembly 414 shown in the embodiment of FIG. 4 is a remoteelectrode assembly that is outside of or otherwise separate from theelectro-reaction cell 420. The electrode assembly 414 can include anelectrode compartment 450, an interface element 460 in the electrodecompartment 450, and an electrode 470 disposed relative to the interfaceelement 460. In an alternative embodiment, the interface element 460 isexcluded such that the electrode 470 is exposed directly to theprocessing solution in the compartment 450. The electrode compartment450 can be spaced apart from the electro-reaction cell 420 within thehousing 410 (as shown in FIG. 4), or in an alternate embodiment (notshown) the electrode compartment 450 can be spaced outside of thehousing 410. The electrode compartment 450 can extend above the housing410 so that the electrode 470 can be easily serviced without having tomove the head assembly 150. The remote location of the actual electrode470 outside of the electro-reaction cell 420 solves the problem ofaccessing the actual electrode 470 for service or repair because thehead assembly 150 does not obstruct the electrode assembly 414. This isexpected to reduce the cost of operating the processing tool 100 (FIG.2) because it will require less time to service/repair the electrodes,which will allow more time for the tool 100 to be available forprocessing workpieces.

The interface element 460 can inhibit particulates and bubbles generatedby the electrode 470 from passing into the processing solution flowingthrough the fluid passageway 416 and into the electro-reaction cell 420.The interface element 460, however, allows electrons to pass from theelectrode 470 and through the electrolytic processing solution PS in theprocessing chamber 400. The interface element 460 can be a filter, anion membrane, or another type of material that selectively inhibitsparticulates and/or bubbles from passing out of the electrode assembly414. The interface element 460, for example, can be cylindrical,rectilinear, two-dimensional or any other suitable shape that protectsthe processing solution PS from particles and/or bubbles that may begenerated by the electrode 470.

The electrode 470 can be a bulk electrode or a solid electrode. When theelectrode 470 is a nickel-sulfur electrode, it is advantageous to use abulk electrode material within the interface element 460. By using bulkNi—S electrode material, the processing station 120 does not need tohave solid, shaped electrodes formed by expensive electroformingprocesses. The bulk Ni—S electrode is expected to be approximately twoorders of magnitude less than a solid, shaped Ni—S electrode. Moreover,because the bulk electrode material is contained within the interfaceelement 460, the pellets of the bulk electrode material are contained ina defined space that entraps particulates and bubbles. Another benefitof this embodiment is that the bulk electrode material not only reducesthe cost of Ni—S electrodes, but it can also be easily replenishedbecause the electrode assemblies 414 are outside of the electro-reactioncell 420. Thus, the combination of a remote electrode assembly, abulk-material electrode, and a virtual electrode unit is expected toprovide a chamber that performs as if the actual electrode is in theelectro-reaction cell for precise processing without having expensivesolid, shaped electrodes or the inconvenience of working around the headassembly.

The processing station 120 can plate or deplate metals, electrophoreticresist, or other materials onto a workpiece 101 carried by the headassembly 150. In operation, a pump 480 pumps the processing solutionthrough a particle filter 490 and into the electrode compartment 450. Inthis embodiment, the processing solution PS flows through a channel 452adjacent to the interface element 460, and then through the fluidpassageway 416 and the flow distributor 440 until it reaches theelectro-reaction cell 420. The processing solution PS continues to flowthrough the electro-reaction cell 420 until it crests over a weir, atwhich point it flows into the tank 410. The primary flow of theprocessing solution PS accordingly does not flow through the interfaceunit 460, but rather around it. A portion of the processing solution PSflowing through the electrode compartment 450 may “backflow” through theinterface element 460 and across the electrode 470 (arrow B). Theportion of the processing solution PS that backflows through theinterface element 460 can exit through an outflow (arrow 0) and returnto the tank 410. The backflow portion of the processing solution PS thatcrosses over the electrode 470 replenishes ions from the electrode 470to the bath of processing solution PS in the tank 410.

The electrons can flow from the electrode 470 to the workpiece 101, orin the opposite direction depending upon the particular electricalbiasing between the workpiece 101 and the electrode 470. In the case ofplating a metal onto the workpiece 101, the electrode 470 is an anodeand the workpiece 101 is a cathode such that electrons flow from theelectrode 470 to the workpiece 101. The electrons can accordingly flowthrough the interface element 460. It will be appreciated that theconductivity of the processing solution PS allows the electrons to movebetween the electrode 470 and the workpiece 101 according to theparticular bias of the electrical field.

FIGS. 5A and 5B illustrate a processing chamber 500 that can be used inthe processing station 120 in accordance with an embodiment of theinvention. Referring to FIG. 5A, the processing chamber 500 includes ahousing or tank 510, a reaction vessel 512 in the tank 510, and aplurality of electrode assemblies 514 outside of the reaction vessel512. The electrode assemblies 514 are identified individually byreference numbers 514 a-514 d, but they are collectively referred to byreference number 514. The electrode assemblies 514 are separate from thereaction vessel 512 to provide easy access to the electrodes for thereasons explained above. In this embodiment, the electrode assemblies514 have a lower portion in the tank 510 and an upper portion above orat least exposed at the top of the tank 510.

FIG. 5B is an isometric view that further illustrates several of thecomponents of the processing chamber 500. The reaction vessel 512includes a electro-reaction cell 520, and a virtual electrode unit 530including a plurality of individual dielectric partitions that formopenings defining virtual electrodes. In this embodiment, the virtualelectrode unit 530 includes a first partition 532, a second partition534 spaced apart from the first partition 532, and a third partition 536spaced apart from the second partition 534. A first virtual electrodeVE₁ is defined by the circular opening inside the first partition 532; asecond virtual electrode VE₂ is defined by the annular opening betweenthe first partition 532 and the second partition 534; and a thirdvirtual electrode VE₃ is defined by the annular opening between thesecond partition 534 and the third partition 536. It will be appreciatedthat the partitions, and hence the virtual electrodes, can have othershapes, such as rectilinear or non-circular curvatures to define anelectric field according to the particular parameters of the workpiece.The electro-reaction cell 520 also includes a weir 538 over which theprocessing solution PS can flow (arrow F) during processing.

The processing chamber 500 can further include a plurality of fluidpassageways 540 and flow distributor 550 coupled to the fluidpassageways 540. Each electrode assembly 514 a-f is coupled to acorresponding fluid passageway 540 so that fluid flows from eachelectrode assembly 514 and into the flow distributor 550. Theelectro-reaction cell 520 can be coupled to the flow distributor 550 bya transition section 560. The flow distributor 550 and the transitionsection 560 can be configured so that the processing solution PS flowsfrom particular electrode assemblies 514 a-f to one of the virtualelectrode openings VE₁-VE₃.

The particular flow path from the electrode assemblies 514 to thevirtual electrode openings are selected to provide a desired electricalpotential for each one of the virtual electrodes VE₁-VE₃ and masstransfer at the workpiece (e.g., the weir 538). In one particularembodiment, a first flow F₁ of processing solution through the firstvirtual electrode VE₁ opening comes from the electrode assemblies 514 band 514 e; a second flow F₂ through the second virtual electrode openingVE₂ comes from the electrode assemblies 514 c and 514 d; and a thirdflow F₃ through the third virtual electrode VE₃ opening comes from theelectrode assemblies 514 a and 514 f. The particular selection of whichelectrode assembly 514 services the flow through a particular virtualelectrode opening depends upon several factors. As explained in moredetail below, the particular flows are typically configured so that theyprovide a desired distribution of electrical current at each of thevirtual electrode openings.

FIG. 6 is a cross-sectional view of an embodiment of the processingchamber 500 shown in FIGS. 5A and 5B taken along line 6-6 (FIG. 5A). Theelectro-reaction cell 520 of the reaction vessel 512 can be defined bythe partitions 532, 534 and 536 of the virtual electrode unit 530 andthe transition section 560. In operation, the workpiece (not shown) isheld proximate to the weir 538 so that the flow of processing solutionover the weir 538 contacts at least one surface of the workpiece.

The reaction vessel 512 can also include a diffuser 610 projectingdownward from the first partition 532. The diffuser 610 can have aninverted frusto-conical shape that tapers inwardly and downwardly withinin a fluid passage of the flow distributor 550. The diffuser 610 caninclude a plurality of openings, such as circles or elongated slots,through which the processing solution can flow radially inwardly andthen upwardly through the opening that defines the first virtualelectrode VE₁. In this particular embodiment, the openings 612 areangled upwardly to project the flow from within the flow distributor 550radially inwardly and slightly upward. It will be appreciated that thediffuser 610 can have other embodiments in which the flow is directedradially inwardly without an upward or downward component. Additionally,the diffuser 610 may also be eliminated from certain embodiments.

The electrode assemblies 514 b and 514 e can be similar or evenidentical to each other, and thus only the components of the electrodeassembly 514 e will be described. The electrode assembly 514 e caninclude a casing or compartment 620, an interface element 622 inside thecasing 620, and a basket 624 inside the interface element 622. Asexplained above, the interface element 622 can be a filter, an ionmembrane, or another type of material that allows electrons to flow toor from the electrode assembly 514 e via the processing solution. Onesuitable material for the interface element 622 is a filter composed ofpolypropylene, Teflon®, polyethersulfone, or other materials that arechemically compatible with the particular processing solution. In theembodiment shown in FIG. 6, the interface element 622 is a cylindricalmember having a bore. The basket 624 can also be a cylindrical,electrically conductive member that fits within the bore of theinterface element 622. The basket 624 is perforated with a plurality ofholes (not shown in FIG. 6) or otherwise porous. In an alternateembodiment, the interface element 622 can be a basket without a filter.

The electrode assembly 514 e can further include a lead 630 coupled tothe basket 624 and an electrode 640 in the basket 624. In the embodimentshown in FIG. 6, the electrode 640 is a bulk electrode comprising aplurality of pellets 642, such a spheres or button-shaped members. Thepellets 642 in FIG. 6 are formed from the desired material for theelectrode. Several applications use a bulk electrode material thatreplenishes the processing solution with the desired ions for platingmaterial onto the workpiece. It will be appreciated that the bulkelectrode materials can be consumable or inert in the processingsolution depending upon the particular application. In alternateembodiments, the electrode 640 can be a solid electrode instead of abulk electrode material composed of a plurality of pellets.

In the embodiment shown in FIG. 6, the electrode assembly 514 e has afluid fitting 650 to receive a flow of filtered processing solution fromthe particle filter, and a gap 652 between the fitting 650 and theinterface element 622. The gap 652 defines the primary fluid flow paththrough the electrode assembly 514 e. In the embodiment shown in FIG. 6,the fluid flows in through the fitting 650, along the flow path 652around the exterior of the interface element 622, and then through thefluid passageway 540 to reach the diffuser 610. A portion of theprocessing solution can back flow (arrow BF) through the interfaceelement 622. The backflow portion of the processing solution can producean outflow (arrow OF) that exits the electrode assembly 514 e through anaperture 660. The outflow OF from the electrode assembly 514 e canreplenish ions for the processing solution PS in the tank 510. Theprocessing solution is then recycled to the pump so that it can befiltered by the particle filter and then returned to the electrodeassemblies 514. Electrons from the bulk electrode material 640 flowthrough the interface element 622 (arrow “e”) via the processingsolution PS. As a result, the electrical charge placed on the lead 514 ecan be controlled to adjust the current gradient in the electrical fieldat the rim of the first partition 532 that defines the first virtualelectrode VE₁.

FIG. 7 is an isometric, cross-sectional view of the processing chamber500 illustrating a flow path of the processing solution through thethird virtual electrode opening VE₃. It will appreciated that commonnumbers refer to like components in FIGS. 6 and 7. The cross-sectionalportion in FIG. 7 shows the flow distributor 550 and the transitionsection 560 directing the flow F of processing solution PS through thefluid passageway 540 and into a channel 710 of the flow distributor 550.The channel 710 directs the fluid flow to an annular conduit 715 definedby the transition section 560. The third flow F₃ of the processingsolution PS then flows upwardly through the annular opening defining thethird virtual electrode VE₃. The flow distributor 550 and the transitionsection 560 operate in a similar manner to direct the fluid from theelectrode assembly 514 f to an opposing side of the annular conduit 715defining the third virtual electrode VE₃. In this embodiment, the flowof processing solution going to the opening of the third virtualelectrode VE₃ does not pass through the diffuser 610. It will beappreciated that the flow distributor 550 and the transition section 560can operate in a similar manner to direct the flow of processingsolution from the electrode assemblies 514 c and 514 d (shown in FIG.5B) to an annular conduit 717 defined by the inner transition piece 560and the first partition 532 of the virtual electrode unit 530. The flowsfrom the electrode assemblies 514 c and 514 d accordingly enter atopposite sides of the annular conduit 717 and then flow upwardly throughthe annular opening between the first and second partitions 532 and 534that define the second virtual electrode VE₂.

Referring to FIGS. 6 and 7 together, each of the electrode assemblies514 can be coupled to the flow from the particle filter via a controlvalve 690, and each of the leads 630 can be coupled to an independentlycontrolled electrical current. As such, the fluid flows F₁-F₃ throughthe virtual electrodes VE₁-VE₃ can be independently controlled, and theparticular current at each of the virtual electrodes VE₁-VE₃ can also beindependently controlled. In one embodiment, the first fluid flow F₁ hasa much higher flow rate (volumetric and/or velocity) than the second andthird fluid flows F₂ and F₃ such that the first fluid flow F₁ dominatesthe mass transfer and flow characteristics at the weir 538. The gradientof electrical current at the openings of the virtual electrodes VE₁-VE₃can be controlled to provide a desired current distribution at thesurface of the workpiece. Suitable programs and methods for controllingthe individual electrical currents for each of the virtual electrodesVE₁-VE₃ are described in detail in PCT Publication Nos. WO00/61837 andWO00/61498; and U.S. application Ser. Nos. 09/849,505; 09/866,391; and09/866,463.

The processing chamber 500 is expected to be cost efficient tomanufacture and maintain, while also meeting stringent performancespecifications that are often required for forming layers from metal orphotoresist on semiconductor wafers or other types of microelectronicworkpieces. One aspect of several embodiments of the processing chamber500 is that bulk electrode materials can be used for the electrodes.This is particularly useful in the case of plating nickel because thecost of nickel-sulfur bulk electrode materials is significantly lessthan the cost of solid, shaped nickel-sulfur electrodes formed usingelectroforming processes. Additionally, by separating the electrodeassemblies 514 from the electro-reaction cell 520, the head assembly orother components inside of the cell 520 do not need to be moved forelectrode maintenance. This saves time and makes it easier to servicethe electrodes. As a result, more time is available for the processingchamber 50 b to be used for plating workpieces. Moreover, severalembodiments of the processing chamber 500 achieve these benefits whilealso meeting demanding performance specifications. This is possiblebecause the virtual anode unit 530 shapes the electrical field proximateto the workpiece in a manner that allows the remote electrodes in theelectrode assemblies 514 to perform as if they are located in theopenings of the virtual electrode unit 530. Therefore, severalembodiments of the processing chamber 500 provide for cost effectiveoperation of a planarizing tool while maintaining the desired level ofperformance.

Another feature of several embodiments of the processing chamber 500 isthat commercially available types of filters can be used for theinterface element. This is expected to help reduce the cost ofmanufacturing the processing chamber. It will be appreciated, however,that custom filters or membranes can be used, or that no filters may beused.

Another aspect of selected embodiments of the processing chamber 500 isthat the tank 510 houses the reaction vessel 512 in a manner thateliminates return plumbing. This frees up space within the lower cabinetfor pumps, filters and other components so that more features can beadded to a tool or more room can be available for easier maintenance ofcomponents in the cabinet. Additionally, in the case of electrolessprocessing, a heating element can be placed directly in the tank 510 toprovide enhanced accuracy because the proximity of the heating elementto the reaction vessel 512 will produce a smaller temperature gradientbetween the fluid at the heating element and the fluid at the workpiecesite. This is expected to reduce the number of variables that can affectelectroless plating processes.

Still another aspect of several embodiments of the processing chamber500 is that the virtual electrode defined by the virtual electrode unit530 can be readily manipulated to control the plating process moreprecisely. This provides a significant amount of flexibility to adjustthe plating process for providing extremely low 3-σ results. Severalaspects of different configurations of virtual electrode units andprocessing chambers are described in PCT Publication Nos. WO00/61837 andWO00/61498; and in U.S. application Ser. Nos. 09/849,505; 09/866,391;09/866,463; 09/875,365; Ser. No. 09/872,151; all of which are hereinincorporated by reference in their entirety.

FIG. 8 is a schematic diagram of a processing chamber 800 for use in theprocessing station 120 in accordance with another embodiment of theinvention. The processing chamber 800 is similar to the processingchamber 400 described above with reference to FIG. 4, and thus likereferences numbers refer to like components. The processing chamber 800is different than the processing chamber 400 in that the processingsolution in the processing chamber 800 flows from the particle filter490 into the electrode compartment 450 and through the interface element460 to flow past the electrode 470. The processing solution then flowsout through the interface element 460 and to the reaction vessel 412 viathe fluid passageway 416. The processing chamber 800 can accordingly bevery similar to the processing chamber 500 described above withreference to FIGS. 5-7, but the processing solution in the processingchamber 800 would not necessarily flow through the gap 652 (FIG. 6) inthe bottom of the electrode compartment 620, but rather it would flowdirectly up into the interface membrane 622. Accordingly, differentembodiments of the invention can have different fluid flows aroundand/or through the interface element 622.

FIG. 9 is a schematic diagram illustrating a processing chamber 900 inaccordance with another embodiment of the invention. In this embodiment,the processing chamber 900 includes a reaction vessel 912 that itselfdefines the electro-reaction cell and a virtual electrode unit 930 inthe reaction vessel 912. The processing chamber 900 can further includeat least one electrode assembly 914 having an interface element 960 anda bulk material electrode 970 in the interface element 960. Theparticular embodiment of the processing chamber 900 shown in FIG. 9includes a plurality of electrode assemblies 914 a and 914 b. The firstelectrode assembly 914 a includes a first interface element 960 adefined by a toriodal tube and a bulk material electrode material 970 acomprising a plurality of pellets inside the toriodal interface element960 a. The second electrode assembly 914 b can be similar to the firstelectrode assembly 914 a. The interface element 960 can be a filter ormembrane without a basket, a basket without a filter or membrane, or abasket surrounded by a filter or membrane. The first electrode assembly914 a can be positioned in an outer section of the reaction vessel 912,and the second electrode assembly 914 b can be positioned in an innerportion of the reaction vessel 912. The processing chamber 900accordingly does not have separate remote electrodes that are outside ofthe reaction vessel 912, but it does include bulk material electrodes incombination with a virtual electrode reactor. It is expected that theprocessing chamber 900 will have some of the same benefits as thosedescribed above with reference to the processing chambers 400, 500 and800, but it does not provide the easy access to the electrodes formaintenance or repair.

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but that various modifications may be made without deviating from thespirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

1-39. (canceled)
 40. A processing chamber for electrochemical processingof a microelectronic workpiece, comprising: a housing; a reaction vesselin the housing, the reaction vessel having a processing site configuredto receive a workpiece during processing; a remote electrode holderincluding a casing in the housing but outside of the reaction vessel, aninlet, an outlet, and an interface member in the casing configured toinhibit at least one of particulates and bubbles in a processingsolution from passing across the interface member, wherein the interfacemember has a cavity; and a conductive electrode in the cavity of theinterface element.
 41. The processing chamber of claim 40, wherein theinterface member comprises a filter.
 42. The processing chamber of claim40, wherein the interface member comprises an ion-exchange membrane. 42.The processing chamber of claim 40, further comprising a conductivebasket in the cavity of the interface member, and wherein the electrodeis in the conductive basket.
 43. The processing chamber of claim 40,wherein the interface member is cylindrical.
 44. The processing chamberof claim 40, wherein the interface member is rectilinear.
 45. Theprocessing chamber of claim 40, wherein the electrode comprises a bulkmaterial having a plurality of pellets.
 46. The processing chamber ofclaim 40, wherein the electrode comprises a solid piece of conductivematerial.
 47. The processing chamber of claim 40, wherein the interfacemember and the basket have sidewalls defining a hollow, and theelectrode is positioned in the hollow.
 48. A processing station forelectrochemically processing a workpiece, comprising: a head configuredto hold a workpiece and move the workpiece to a processing site; aprocessing chamber having a housing, a reaction vessel in the housingconfigured to direct a flow of processing solution to the processingsite, and a remote electrode compartment having a casing and aninterface member in the casing, wherein the interface member isconfigured to inhibit at least one of particulates and bubbles frompassing across the interface member, and wherein the casing is in thehousing but outside of the reaction vessel at a location at which theinterface member is accessible from above the reaction vessel and to aside of the head; and a conductive electrode received within theinterface member.
 49. An electrode assembly for use in anelectrochemical reaction vessel, comprising: a casing having an inletthrough which a processing solution can enter the casing and an outletthrough which the processing solution can exit the casing; an interfacemember in the casing, the interface member being configured to inhibitat least one of particulates and bubbles from passing across theinterface member, and the interface member having a cavity; a conductivebasket in the cavity of the interface member, wherein the basket has asidewall and bottom defining an interior and the basket is removablefrom the interface member; and a conductive electrode in the basket. 50.An electrode assembly for use in an electrochemical reaction vessel,comprising: a casing having a lower portion, an inlet in the lowerportion of the casing through which a processing solution can enter thecasing, a first outlet in the lower portion of the casing through whicha primary flow of processing solution can enter the reaction vessel, anupper portion, and a second outlet in the upper portion of the casingthrough which a back flow of processing solution can exit the casing; aninterface member in the casing, the interface member having a cavity andbeing configured to inhibit at least one of particulates and bubblesfrom passing across the interface member; a passageway between the inletand the casing through which the primary flow of processing solution canflow to the first outlet; and a conductive electrode in the cavity ofthe interface member.